Power density for an electric motor is related to the size of a rotor and stator. Typically, to increase power density, the size of the rotor and stator have to be correspondingly increased. However, the electric motors can be liquid cooled to increase power density without also having to increase the size of the rotor and stator. Liquid cooling permits higher motor currents for the same size rotors and stators that are not cooled.
Motor cooling jackets are used to provide the liquid cooling. One known motor cooling jacket comprises a single-piece cast component with cast-in-place cooling tubes. This type of cooling jacket is disadvantageous because cast tooling is costly and has long lead times. Also, cast tooling is inflexible in that each different motor configuration requires a unique casting. Further, the cast-in-place cooling tubes are limited in cooling capability.
Cast cooling jackets have traditionally been enclosed at opposing ends with end caps. Coolant flows through the end caps and through channels formed within the jacket. The end caps have to be formed or machined to include fluid channels to permit return fluid flow through the cooling jacket to the opposite end cap. This increases the cost of the cooling jacket.